mongoexport -d test -c user_coll -o /var/www/aizhike/aizhike_DB/user_coll.json
mongoexport -d test -c strategy_coll -o /var/www/aizhike/aizhike_DB/strategy_coll.json
mongoexport -d test -c subscribe_coll -o /var/www/aizhike/aizhike_DB/subscribe_coll.json
mongoexport -d test -c comment_coll -o /var/www/aizhike/aizhike_DB/comment_coll.json
